The influence of thermal process of coloured potatoes on the content of glycoalkaloids in the potato products

Potato products made from potato varieties with coloured flesh (red and blue-fleshed potatoes) may be an interesting alternative to traditional products. The purpose of this study was to determine the influence of peeling, cooking and frying of red and blue-fleshed potato tubers on the content of glycoalkaloids (alpha-solanine and alpha-chaconine) in processed potato products. The material taken for the study consisted of seven coloured potato varieties. French fries and crisps were prepared from two potato variety: Rosalinde and Blue Congo. The content of total glycoalkaloids (TGA) in raw material before and after peeling, in cooked unpeeled and peeled potatoes and also in fried potato products have been determined by HPLC method. Studied potatoes of seven coloured fleshed varieties contained less than 300 mg kg(-1) d.w. glycoalkaloids. TGA levels in red-fleshed potato varieties were statistically higher by about 8% compared with the blue-fleshed varieties. The proportion between alpha-solanine and alpha-chaconine in potato tubers and in processed potato was found to stabilize in the ranges from 1.0:1.8 (Blue Congo variety) up to 1.0:2.2 (Rosalinde variety), and the highest changes of proportion between alpha-solanine and alpha-chaconine in crisps were stated. The peeling process decreased the TGA content in tubers independently on studied potato variety, in average about 20%, cooking of un-peeled potato about 8% and cooking peeled potato about 39%, comparing with a raw material. Higher decreases of TGA were found in fried products (mean about 83% in crisps, about 92% in French fries after I stage of frying and about 94% in ready French fries). (C) 2011 Elsevier Ltd. All rights reserved.